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What is a laboratory autoclave and how does it work?
In any research, clinical or industrial environment, microbial contamination is the number-one enemy of analytical reliability. Keeping instruments, samples and culture media sterile is not just a recommended practice — it is the foundation on which any validatable result rests.
But what exactly is an autoclave? It is a thick-walled metal vessel with hermetic closure designed to sterilise material via saturated steam at high pressure and temperature. Without question, it is the reference sterilisation equipment in pharmaceutical, clinical and food control laboratories.
In essence, the autoclave serves to fully and reliably inactivate every form of microbial life — including bacteria, spores, viruses and prions — that would otherwise survive less demanding chemical or thermal methods.
At JP Selecta, as scientific instrumentation specialists, we know that autoclave sterilisation remains the most effective, economical and reproducible method to guarantee the laboratory's biological safety.
How does an autoclave work?
To understand what an autoclave is, you must understand its physical principle based on the direct relationship between vapour pressure and saturation temperature.
When water is heated inside the hermetic chamber, the steam generated displaces the interior air. Unable to expand, pressure progressively increases.
This rise allows the inner air to become saturated with steam, far exceeding water's usual boiling point at atmospheric pressure.
A standard sterilisation cycle typically subjects the load to 121 °C under approximately 1 bar pressure for 15–20 minutes — enough to destroy vegetative cells, resistant spores and encapsulated viruses.
Types of autoclave and when to use each
Not every laboratory processes the same materials or has the same volumetric needs. A standardised classification of autoclaves therefore exists, responding to both load type and equipment geometry.
Knowing the differences between the various types of sterilisation autoclave is crucial to guarantee process effectiveness and corresponding regulatory compliance.
To simplify their classification, we divide equipment under two essential criteria: by load type and by physical design.
Autoclaves by load type (Type N, S and B)
The Type N autoclave is the simplest device on the market. It is designed exclusively to sterilise bare solid material (unwrapped), such as unbagged surgical instruments or glass pieces. Without advanced vacuum systems, it cannot effectively extract air trapped in porous materials.
Type S autoclaves represent an intermediate range with more flexible performance. Although specifications depend on the manufacturer, they can generally process both solid load and certain bagged materials or light textiles, always under specific manufacturer indications.
The Type B autoclave is the gold standard in versatility and biosafety. The term "B" stands for Big small steriliser. These units integrate fractionated multi-pulse vacuum systems before steam entry, ensuring saturated steam fully penetrates porous materials, hollows, cannulas or wrapped textiles. It is the only one capable of sterilising every type of load per EN 13060.
Autoclaves by design and structure
- Benchtop or portable autoclaves: compact units ideal for direct placement on benches or work surfaces. Suitable for dental clinics, small laboratories and teaching centres.
- Vertical autoclaves: classic in microbiology and quality control laboratories. Top access eases loading of tall flasks and culture media.
- Large-capacity autoclaves: ideal for massive research centres or industrial production environments. Within the JP Selecta group, Steril Food covers industrial food sterilisation with autoclaves up to 150 L.
- Pulsating-vacuum (pre-vacuum) autoclaves: advanced mechanical systems using repeated cycles of steam injection and air extraction to ensure full penetration in porous loads, per EN 285 in hospital applications.
How to know which autoclave your laboratory needs
Now that you know what an autoclave is and the options it offers, apply this guide to identify which autoclave types best suit your needs. Simply answer these questions:
What exactly will you sterilise?
The nature of your material dictates the technology you need. If you only work with bare solid material, a Type N may be enough.
For mixed loads or wrapped instruments, you must move up to a Type S like the Autester ST DRY-S. However, if your daily routine involves textiles, cannulas, porous materials or wrapped sterile medical products, Type B is mandatory.
An important detail: if you introduce liquids in hermetically sealed containers, you will need an autoclave with counter-pressure system to avoid violent liquid boiling upon depressurisation.
How many cycles do you run per day?
The chamber should not be chosen solely by the physical size of the largest load — it should be chosen strategically based on daily processing volume.
For example, a 23-litre benchtop autoclave may be more than enough to handle 2–3 daily cycles in a dental clinic.
However, if sample volume is continuous or you have several work lines running in parallel, purchasing should orient toward a vertical or double-door 80–150 L autoclave that optimises the laboratory's operational flow.
Does your sector demand GMP, FDA or EN 285 compliance?
Depending on your industry (pharmaceutical, sanitary or food), regulatory requirements change radically.
In these high-responsibility sectors, you mandatorily need fully validatable equipment under IQ/OQ/PQ protocols with 21 CFR Part 11 control software and complete documentary traceability. More information in our post on GMP and FDA standards in the laboratory.
In audited environments, an autoclave without integrated documentation capability simply will not pass an audit under current standards.
Therefore make sure the equipment strictly meets international manufacturing standards such as ISO 13485 (medical) or EN 285 (large sterilisers).
Do you have technical service nearby?
The real cost of a unit does not end at purchase. You must evaluate in advance key operational factors such as water and energy consumption, availability of original spare parts and technical service response time.
Acquiring an excessively cheap unit lacking official technical support in Spain can end up costing dramatically more in the medium term due to unplanned downtime and import dependency.
Conclusion: the right autoclave for your laboratory
Choosing the right autoclave is the foundation that keeps your laboratory's processes at the highest standards of biosafety and documentary traceability.
At JP Selecta we design and manufacture autoclaves from 8 to 150 L under triple ISO 9001, ISO 14001 and ISO 13485 certification, with documentation ready for IQ/OQ. See our full autoclave range or contact our technical team for a personalised recommendation based on your sector and workload.